This invention relates to an axle assembly having multiple wheels at each end of the axle in which one wheel on one axle end is permitted to rotate relative to the other wheels on the same axle end. More specifically, the invention relates to bearing members that support adjacent wheel hubs to achieve independent relative rotation during turns.
Axle assemblies have typically incorporated dual wheels on either end of the axle to increase the load bearing capacity for heavy duty vehicles. Typically the pair of wheels on each end of the axle assembly is secured together so that they rotate at the same speed about an axis even during turns. Most off-highway vehicles, such as lift trucks, container handlers, front end loaders, etc., have duty cycles that include numerous turning maneuvers, which cause significant tire wear. The tire wear is a direct result of tire scrub, or drag, caused by wheels that are rigidly secured together for rotation at the same speed but which must travel different distances at the inside and outside of the turning radius. Tire wear and maintenance on heavy duty off-highway vehicles due to scrub cost thousands of dollars annually per vehicle.
Additionally, tire scrub reduces vehicle stability during turning maneuvers. As a vehicle moves through a turn, tire scrub detracts from the net ground coefficient necessary for traction, braking, and side forces in turns. Tire scrub also causes premature wear of various wheel end components, such as wheel rims. The wheel rims can fail prematurely due to added stresses caused by repeated tire scrub. Finally, tire scrub increases fuel consumption as well as powertrain wear and tear in drive axles.
For the above reasons, it would be desirable to reduce tire scrub by having a wheel end that allows adjacent wheel hubs to rotate independently relative to one other to allow each tire to rotate at different speeds through a turn.